linux-kernel - [tip:locking/core] Revert "sched/core: Take the hotplug lock in sched_init

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Date:   Mon, 21 Jan 2019 03:30:45 -0800
From:   tip-bot for Valentin Schneider <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     valentin.schneider@....com, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, paulmck@...ux.vnet.ibm.com,
        torvalds@...ux-foundation.org, hpa@...or.com, peterz@...radead.org,
        will.deacon@....com, akpm@...ux-foundation.org, mingo@...nel.org
Subject: [tip:locking/core] Revert "sched/core: Take the hotplug lock in
 sched_init_smp()"

Commit-ID:  b5a4e2bb0f4c86bfeb38df3e1d5b2f1272f0e673
Gitweb:     https://git.kernel.org/tip/b5a4e2bb0f4c86bfeb38df3e1d5b2f1272f0e673
Author:     Valentin Schneider <valentin.schneider@....com>
AuthorDate: Wed, 19 Dec 2018 18:23:16 +0000
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Mon, 21 Jan 2019 11:18:54 +0100

Revert "sched/core: Take the hotplug lock in sched_init_smp()"

This reverts commit 40fa3780bac2b654edf23f6b13f4e2dd550aea10.

Now that we have a system-wide muting of hotplug lockdep during init,
this is no longer needed.

Signed-off-by: Valentin Schneider <valentin.schneider@....com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Will Deacon <will.deacon@....com>
Cc: cai@....us
Cc: daniel.lezcano@...aro.org
Cc: dietmar.eggemann@....com
Cc: linux-arm-kernel@...ts.infradead.org
Cc: longman@...hat.com
Cc: marc.zyngier@....com
Cc: mark.rutland@....com
Link: https://lkml.kernel.org/r/1545243796-23224-3-git-send-email-valentin.schneider@arm.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/sched/core.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b05eef7d7a1f..3c8b4dba3d2d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5867,14 +5867,11 @@ void __init sched_init_smp(void)
 	/*
 	 * There's no userspace yet to cause hotplug operations; hence all the
 	 * CPU masks are stable and all blatant races in the below code cannot
-	 * happen. The hotplug lock is nevertheless taken to satisfy lockdep,
-	 * but there won't be any contention on it.
+	 * happen.
 	 */
-	cpus_read_lock();
 	mutex_lock(&sched_domains_mutex);
 	sched_init_domains(cpu_active_mask);
 	mutex_unlock(&sched_domains_mutex);
-	cpus_read_unlock();
 
 	/* Move init over to a non-isolated CPU */
 	if (set_cpus_allowed_ptr(current, housekeeping_cpumask(HK_FLAG_DOMAIN)) < 0)